Patent application WO 2005/055655 A1 discloses a hearing aid with a casing intended to be worn behind the ear of a user and a tube leading sound from a receiver, i.e. a loudspeaker, in the casing to the ear canal of the user. The term “Behind-The-Ear” or “BTE” is commonly used to designate this type of hearing aids. A similar type of hearing aids, commonly designated as “Receiver-In-The-Ear” or “RITE”, has the receiver or loudspeaker arranged in the ear canal, and instead of a tube, an electric connection leads an audio signal from an amplifier in the casing to the loudspeaker. For both of these hearing-aid types, it is commonly known to arrange a portion of the casing on the top of the ridge between the pinna and the head, i.e. where the temple bar of spectacles normally rests. One or more microphones are preferably arranged in this portion of the casing such that sounds from the user's environment may be picked up relatively undisturbed by the pinna. In the hearing aid disclosed in WO 2005/055655 A1, two such microphones are arranged in said portion of the casing, which allows for providing various forwards- and/or backwards-oriented directional microphone signals by combining the outputs of the two microphones.
Patent application EP 1 587 343 A2 discloses a hearing aid with an RF antenna constituted by a metallic layer in the casing material or on the casing surface and which thus does not take up space within the housing. In one embodiment, the antenna is coiled around the same portion of the housing in which microphones are preferably arranged as explained above. Connecting the disclosed antenna to an RF transmitter and/or receiver within the casing may require handling delicate and fragile wires.
Patent application US 2009/0262970 A1 discloses a headset in which a cable connecting a microphone PCB and a connector comprises an antenna wire for receiving FM radio broadcasts as well as a number of audio wires. The audio wires are decoupled at the connector end of the cable by means of ferrite beads. The headset antenna is not suitable for receiving or transmitting RF signals in the GHz range.
Patent application US 2009/0033574 A1 discloses a headset in which a cable connecting a loudspeaker and a connector comprises an antenna wire for receiving FM radio broadcasts as well as a number of audio wires. The audio wires are decoupled at the connector end of the cable by means of inductors. The headset antenna is not suitable for receiving or transmitting RF signals in the GHz range.
Patent application EP 2 230 718 discloses an earphone receiver. The device includes a tuner unit that receives broadcast waves. A multi-core shielded cable is used as an antenna.
In hearing devices and in other kinds of electronic devices, it is often desirable to arrange an RF antenna close to other electronic components, which are not directly involved in the RF reception or RF transmission, such as e.g. a microphone, e.g. in order to save space or provide a smooth outer surface of the device without protruding antennas. Electronic components and other electrically conductive elements arranged close to the RF antenna may, however, disturb the latter, thereby deteriorating the antenna matching and thus decreasing the total radiation efficiency, i.e. the sum of the radiation efficiency and any mismatch losses. The problem more or less scales with the wavelength of the RF signals. For instance, at 2.4 GHz, which is e.g. used for Bluetooth signals, the wavelength is about 12 cm, and a quarter-wavelength antenna has a length of about 3 cm. In this case, a distance of about 3 mm, i.e. about 2.4% of the wavelength, or more to other electrically conductive parts is required to avoid disturbances. Maintaining such a minimum distance in a small apparatus, such as a hearing device intended to be worn at an ear, may significantly increase the size of the apparatus and/or put undesired constraints on the placement of further components within the apparatus.